Does Lest Have The Same Meaning As Unless?

No, it doesn't. "Lest" is an old word, almost out of use now. You only really find it in poetic expressions like "Lest we forget" (often used in connection with the soldiers who died in World War I, though the phrase actually comes from an older poem by Rudyard Kipling.) The nearest equivalents in modern English would be "in case" or "for fear that" and it is always followed by a subject and a verb. An example sentence might be:

I daren't touch the china vase, lest I break it. (ie., I am so afraid of breaking it that I won't touch it.

"Unless" has the same position in a sentence, but means "if not." Example sentences could be:

I'll go for a picnic tomorrow unless it rains (ie., if it doesn't rain)

I won't go unless you do (ie., if you don't go.)